linux-kernel - [PATCH] i2c: at91: use dma safe buffers

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Date:   Thu,  3 Mar 2022 17:17:24 +0100
From:   Michael Walle <michael@...le.cc>
To:     Codrin Ciubotariu <codrin.ciubotariu@...rochip.com>,
        Nicolas Ferre <nicolas.ferre@...rochip.com>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        Claudiu Beznea <claudiu.beznea@...rochip.com>,
        Sumit Semwal <sumit.semwal@...aro.org>,
        Christian König <christian.koenig@....com>
Cc:     linux-i2c@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, linux-media@...r.kernel.org,
        dri-devel@...ts.freedesktop.org, linaro-mm-sig@...ts.linaro.org,
        Michael Walle <michael@...le.cc>, stable@...r.kernel.org
Subject: [PATCH] i2c: at91: use dma safe buffers

The supplied buffer might be on the stack and we get the following error
message:
[    3.312058] at91_i2c e0070600.i2c: rejecting DMA map of vmalloc memory

Use i2c_{get,put}_dma_safe_msg_buf() to get a DMA-able memory region if
necessary.

Cc: stable@...r.kernel.org
Signed-off-by: Michael Walle <michael@...le.cc>
---

I'm not sure if or which Fixes: tag I should add to this patch. The issue
seems to be since a very long time, but nobody seem to have triggered it.
FWIW, I'm using the sff,sfp driver, which triggers this.

 drivers/i2c/busses/i2c-at91-master.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/drivers/i2c/busses/i2c-at91-master.c b/drivers/i2c/busses/i2c-at91-master.c
index b0eae94909f4..a7a22fedbaba 100644
--- a/drivers/i2c/busses/i2c-at91-master.c
+++ b/drivers/i2c/busses/i2c-at91-master.c
@@ -656,6 +656,7 @@ static int at91_twi_xfer(struct i2c_adapter *adap, struct i2c_msg *msg, int num)
 	unsigned int_addr_flag = 0;
 	struct i2c_msg *m_start = msg;
 	bool is_read;
+	u8 *dma_buf;
 
 	dev_dbg(&adap->dev, "at91_xfer: processing %d messages:\n", num);
 
@@ -703,7 +704,18 @@ static int at91_twi_xfer(struct i2c_adapter *adap, struct i2c_msg *msg, int num)
 	dev->msg = m_start;
 	dev->recv_len_abort = false;
 
+	if (dev->use_dma) {
+		dma_buf = i2c_get_dma_safe_msg_buf(m_start, 1);
+		if (!dma_buf) {
+			ret = -ENOMEM;
+			goto out;
+		}
+		dev->buf = dma_buf;
+	}
+
+
 	ret = at91_do_twi_transfer(dev);
+	i2c_put_dma_safe_msg_buf(dma_buf, m_start, !ret);
 
 	ret = (ret < 0) ? ret : num;
 out:
-- 
2.30.2